1. Technical Field
The present invention relates to an actuator, and more particularly, to the configuration of an actuator which can detect a direction of displacement or an amount of displacement.
2. Related Art
A polymer actuator is known as a type of actuator. The actuator is formed of a soft material such as rubber and has a characteristic that it will bend with the application of a voltage and is restored to the original state with the cessation of the voltage application. For example, electrodes are formed on both surfaces of an ion-exchange membrane and a potential difference is given to the ion-exchange membrane to deform the ion-exchange membrane. Examples of a polymer electrolyte-membrane actuator having such a characteristic are described in JP-A-4-275078 and JP-A-11-169393.
However, the polymer actuator generally has a problem in that the response speed is low and the controlling of the displacement is not easy.
The present applicant particularly proposes a polymer actuator which can be made to behave to a desired position by disposing a sensor detecting a potential (potential difference) generated in an electrolyte membrane due to bending in the electrolyte membrane and performing a feedback control operation thereon so as to reduce the size of a structure employing the polymer actuator.
However, the voltage (for example, 2 mV) detected by the sensor is lower than the voltage (for example, 3 V) applied to a driving electrode formed on the electrolyte membrane. When the sensor is disposed close to the driving electrode, the sensor is easily influenced by a drive voltage. When the sensor is disposed apart from the driving electrode, the influence of the drive voltage on the sensor decreases but it is not desirable from the viewpoint of the decrease in size of the entire actuator.